(yet another) switch pop problem

Started by tempus, November 23, 2008, 11:08:20 AM

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tempus

Hey all;

A few years ago I built an FX switching system based on the one at the Geofex site (http://www.geofex.com/Article_Folders/fxswitchr/fxswitchr.htm. I made some modifications to include an A/B bank switch. Also, I have the unit set up so that it can select any combination of (pre-programmed) effects with one stomp. So, I can go from, say, bypass, to clean channel with delay and chorus with only one switch. It works beautifully (thanks RG for posting this at your site) except....

I've never been able to get the switching pop free. I've used relays, CMOS switches, BS170's with the control voltages ramped up, you name it, but I always get a pop when I switch. To make matters worse, sometimes it's a loud pop, other times it's barely noticeable, and it often varies even on the same switching operation. I'm starting to wonder if the problem is in the switching circuitry. Is it possible that the switching is somehow working its way into the audio path? The box containing the circuitry is shielded, but should the wires connecting the pedals be shielded also?

I'd be grateful for any help or ideas that any one may have. I've read some of RG's articles claiming to get NO clicks or pops of any kind. Since I've yet to experience this, I wonder if there's something fundamentally wrong with my design or layout or power supply or...

I can post a schematic of the relays board, but I'm having trouble getting that to work.

Thanks


snap

tempus: better repost your quest in the main forum,
where it will be seen by a lot more people that could help you out.
(this digital part is not beingoverly frequented, and your problem is not a must for this part but rather a crossover problem to the general topics).
hope it helps.